Tank assault

According to a photographer for the AFP news agency, the tanks were followed by several smaller military vehicles believed to be carrying Turkish-backed Syrian rebels.

Shelling began at about 04:00 local time (01:00 GMT), with 224 rounds were fired at 63 targets in the space of one hour and 45 minutes.

Air strikes by Turkish and US planes began just after 06:00, Turkish media report.

Image copyrightAFPImage captionSyrian tanks could be seen manoeuvringImage copyrightEPAImage captionA coach said to be carrying Syrian rebels was spotted by reporters in Karkamis

The Turkish town of Karkamis - just across the border from Jarablus - was evacuated as a precaution following earlier IS mortar attacks.

Turkey has vowed to "completely cleanse" IS from its border region.

"The Turkish Armed Forces and the International Coalition Air Forces have launched a military operation aimed at clearing the district of Jarablus of the province of Aleppo from the terrorist organisation Daesh [IS]," said a statement from the Turkish prime minister's office.

Turkey blames IS for a bomb attack on a wedding that killed at least 54 people in Gaziantep on Saturday.

Fighters from the Syrian Kurd YPG militia led the battle to drive IS out of the strategic crossroads town of Manbij earlier this month.

Turkey views the YPG as an extension of the Kurdistan Workers Party (PKK), a Turkish-Kurdish rebel group fighting for autonomy since the 1980s, but the YPG is backed by the US as one of the most effective forces battling IS.

On Tuesday the YPG took control of most of the north-eastern Syrian city of Hassakeh.

A truce was reportedly brokered by Russia after recent clashes between the Kurds and Syrian government forces there.